Fix for lack of "use" statement in BaseQuery subclasses in single table inheritance when using namespaces

Fix for lack of "use" statement in BaseQuery subclasses in single table inheritance when using namespaces

Requiements to reproduce problem: 
* we are using namespace for all classes generated by Propel
* we have Book class which has subclasses Essay & Comic

Problem description:
* generated BaseEssayQuery class extends BookQuery but it does not have "use" statement for it, so it causes errors when class is used

Solution:
* call class declaration when parent class name is being guessed (it adds required use statement if it wasn't already defined)